Three gear pressure loaded pump



Jan. 6, 1959 H. H. CAMPBELL ETAL 2,867,174

THREE GEAR PRESSURE LOADED PUMP Filed July 22. 1955 frzverzi'ofifil [7272.73/ 15. Campbell and Fran/ 5 C ji'anek 2,867,174 c Patented Jan. 6, 1959 2,867,174 7 rmuzn GEAR PRESSURE LOADED PUMP- Application July 22, 1955, Serial No. 523,804 3 Claims. (Cl. 103-126) This invention relates to a gear pump and more particularly to a gear pump of the type employing pressure loaded bushings or end plates, such pumps sometimes being referred to as pressure loaded pumps.

In pressure loaded pumps of the type including means defining a set of axially movable, pressure loadable bushings or end plates, hereinafter referred to as bushings, a part of the discharge pressure generated by the pump is communicated to the rear or motive pressure surface of the axially movable bushings to urge the bushings into sealing relationship with their associated gears. As described in United States Patent No. 2,420,622 to John A. Lauck et al., by carefully selecting the relative areas of the forward surfaces and the rear or motive surfaces of the bushings, it is possible to control within very close limits the actual sealing pressure established during operation of the pump. Gear pumps so constructed are capable of delivering fluid at an extremely high pressure with considerable volume.

In the aforementioned pressure loaded pump of John A. Lauck et al., there are provided a pair of intermeshing gears for pumping fluid from an inlet to an outlet under pressure, one of the gears comprising a drive gear and the other a driven gear. It has been found that by providing a pump with three gears, one a drive gear and the other two driven gears, it is possible to materially increase the pumping capacity without a corresponding increase in size and weight of the pumping unit. By employing such a tri-gear pump, it is possible to increase the pumping capacity by 100%, with a size and weight increase of only 50%, when compared with the usual two gear pump incorporating the same size gears. It is also evident that a tri-gear pump requires fewer parts for a particular capacity resulting in a saving in material and machining. Therefore, it is the principal object of this invention to provide a pressure loaded pump incorporating three pumping gears; a drive gear and two driven gears.

More particularly, it is an object of this invention to provide a pressure loaded pump having an increased pumping capacity of 100% over the prior art type incorporating the same size gears, yet having a size and weight increase of only 50% thereover.

Still more particularly, an object of this invention is to provide three gear pressure loaded pumps incorporating a drive gear and a pair of driven gears, having an increased pumping capacity of 100% over prior art types incorporating the same size gears, yet having a size and weight increase of only 50% thereover. 1

Further, it may be seen that given a particular capacity, it is possible to construct a tri-gear pump with a saving in mounting space requirements and weight over the prior art type. Therefore, another important object is to provide a pump with a capacity of prior art types yet requiring less mounting space and being lighter in weight.

Other objects and features of this invention will become apparent from the following description when taken with the accompanying drawing, wherein the same reference character is employed to refer to the same part and wherein:

Figure 1 is an axial cross-sectional view of a gear pump constructed in accordance with this invention; and

Figure 2 is a partial sectional view taken on line 22 of Figure 1, looking in the direction of the arrows, and showing to advantage the gear engaging faces of the bushings, and showing diagrammatically the inlets and outlets associated with the pumping gears.

Referring in greater detail to the figures of the drawings, 10 denotes generally a liquid gear pump adapted to be driven from a suitable source of power, such as an aircraft motor (not shown) and incorporating the preferred embodiments of this invention. A main pump housing 11 is formed with parallel overlapping or intersecting cylindrical chambers 12, 13 and 14 receiving gears 15, 16 and 17, the gear 16 meshing with the gears 15 and 17, the meshing occurring in the overlapping areas of the chambers. The gear 16 comprises a drive gear while the gears 15 and 17 comprise driven gears. A housing end wall closure plate 18 is attached to the open end of the housing 11, as by threaded stud bolts 19 (only one of which is shown). The inner exposed surface of the closure member 18 forms end walls 20, 21 and 22 of gear chambers 12, 13 and 14 which end walls extend radially parallel to the opposite end walls 23, 24 and 25, the gears having a co-axial thickness less than the co-axial dimension of chambers 12, 13 and 14 providing annular spaces on both sides of the gears. The gear chamber end walls 20, 21, 22, 23, 24 and 25 are formed with reduced bore extensions 26, 27, 28, 29, 3t) and 31, respectively, and the gears 15, 16 and 17 are provided with oppositely extending coaxial hollow journals 32, 33, 34, 35, 36 and 37 of smaller cross section than the extension bores and received coaxially in said bores.

Of particular importance in pumps of this type is the provision of specially constructed and operated end plates or hearing bushings, these bushings being interposed between the housing and the gears and being constructed of suitable bearing material. There are preferably six of these bushings, each having substantially the same formation and each associated with one of the gear journals. Thusly, bushings 33, 39, 40, 41, 42 and 43 are provided and include tubular portions 44, 45, 46,

47, '48 and 49 received in embraced relation about the gear journals 32, 33, 34, 35, 36 and 37, respectively, and outwardly extending flange terminal portions 50, 51, 52,

53, 54 and 55, respectively, received in the adjacent venting the passage of liquid therebetween. These sealing rings may be disposed within grooves formed in the member 18, as illustrated, or within grooves formed in the bushing tubular portions.

The terminal flanges 50, 52 and 54 are arranged to have a limited axial piston-like operation or adjustment in chambers 12, 13 and 14 adjacent one side of the gears 15, 16 and 17 for bringing the gears 15, 16 and 17 and the flanges 50, 52 and 54, respectively, into sealed contact, which arrangement provides three annular liquid pressure chambers or spaces 57, 57a and ,58 between the end walls 20, 21 and 22 and the back face or side of the adjacent flanges 50, 52 and 54, respectively. The corresponding tubular portions 44, 46 and 48 within the co-axial extensions 26, 27 and 28, respectively, likewise have a limited piston-like adjustment therein. nular pressure chambers 57, 57a and 58 are arranged to be supplied with liquid pressure from the high pressure sideof the gear teethby a specially formed set of conduits to be described in detail. If necessary, the

The air 3 flanges 5 1, 53 and 55 and-the tubular portions 45,47 and.49..may berarrangedfor limited axial-'piston-like operation and adjustment.

The opposite or inner terminal portions of thefianges 59;. 513- 52, 53, 541 and .55 are formed with fmnt or inner radially extending faces 59, 6t 61, 62; 63 anrl 64 parallel; to 1 the adjacent sidefaces of therespective gears 15, 16 and'lland: are arranged to -normally engage the same to provide' apumpinghealtherewith.- Asin thejpressure; loaded pump described in the aforementione patent to Lauck et;al;., it has been found' tiiat where the gear engaging. faces of the bushingshave been .made co-extensive withthe geanproperfrom' a point adjacent the; journal outwardly tothe periphery ofthe gear-teeth, an improper operation ;ofthe-pu;rinpthas resulted. Wh

generally indicated at 71 (see Figure 2) in the areas of meshing of thergear teeth. Due to manufacturingimperfections, the bushing flanges at the terminal portions of surfaces 71 do not always fit accurately, and hence a certain amount of leakage or by-passing of liquid ing place through these imperfections in the fit. As in the aforementioned patent to Lauck et 3.1:, a solution to this problemis provided by theinsertion of closureplugs (not shown).

Main liquid conductingpassages72, 7'3, 74' and 75,

diagrammatically shown in Figure 2, lead to the opposite high pressures are approached-,Ithentthe pressure .g between the, f l,ange;faces and thezadjaccnt; gear feces becomes-sufliciently great to force. the flange away from the gear face resulting in. a dropin volumetric deficiency. While in, the aforementioned patent-Io Lauck et: al., this condition, exists for both gears (there-beingcnly two), it has been found that in the .tri-gearpump of the instant application, this condition exists for only, two gears, namely, the driven gears l5H-and 17. Therefore, the bushing 40 is constructedtoflt; snugly within the bore 27 and between the adjacent gear face and the facev 21 of the chamber 13. The bushing 44 is subject to diametrically opposed balanced high pressures within the pump chamber, the total pressure being of much smaller extent than that to which the bushings 39 and 42 are subjected.

The bushing fac'es59, 60, 63 and 64 are machined to provide smallrecesses 65, 66, 69; and 70 adjacent the juncture of the journals32, 33, 34, 35, 36 and 37, respectively, which function as relief recesses and accomplish asolution of the problems set forth above and are placed in communication with a low pressurezone, as will be described in greater detail hereinafter. For pumps of small displacement, the same results may be obtained byjemploying only the recesses 65 and 6 as relief recesses, and in such case, only these two will be in communication with a zone of low pressure. It isto be expressly understood that the recesses above described may alternatively be formed in the bushing faces of the gears 15 and 17, if so desired.

A very important function of the relief recesses 65 66, 69 and'70- is to reduce the effective pressure areas between the flange front faces 59, 60, 63 and 64 and the adjacent gear radial faces to a value below the effective pressure or axial force acting in the opposite direction off} the back faces of the flanges 5t) and 54 within the annular pressure chambers 57 and 5 8. It is important to' note that. it is only necessary for'this differential of pressure or axial force to be a relatively' low fraction of the total pressure within theannular pressure or axial. forceactingchambers or spaces57' and 58, since as long as a small "differential is maintained, the bushingsv will not be pushed away fromthegear. faces regardless of the extremely high pressure that may be involved. Since the flange 52 is not subjected to ,as high pressures in the. pumping chamber as. the flanges 56 and 54, the pressures in the pressure chamber 57tr will always slightly, exceed that applied'to the flange face 61and'no relief recess is required to maintain the small differential as in the case of the flanges and 54. The, bushing flanges 50, 52

and 54 thushave the pressure on the annular pressure chamber side thereof always slightly predominating to produce an unbalance in the direction of. the gear to maintain thegrequired seal with no excessive pressure which would produce objectionable wear.

Since it isextrernely diflicult to machine the juncture ofqthe gear faces and the gear journals,'gro oves such as 67fand- 68, are provided onall' the gears.

Itwill be seen that each of the-bushing flanges hasat sides of the'gear teeth in the areas of meshing forcon ducting the main flow ofliquid; to the gear" teeth and discharging the same therefrom. More specifically, the passages 72 and 74 function as inlets for the flow of liquid to the meshing gear teeth and the, passages 73 and'74'function asoutlets'for discharge passages forthe flow'of liquid under pressure therefrom. The inlets and outlets may be-connected in any suitable manner to at-' tain the increased output of the tri-gear pump; The direction of'rotation of the'gears is indicated by the ar rows in Figure 2.

In'orderfor the'relief recesses 65, 66, 69 and 70 to perform their function, the same must be placed in communication with a'zone of pressure lower than that existing 'either'at the high pressure side ofthe gear teeth or in the annular pressure chambers 57 and 58. This is accomplished-by placing the relief recesses in com-- munication' with alow pressure zone, which communie cation-is effective by forming the bushings 38, 39, 4'2' and 43 with axially extending-channels or grooves 76,77; 78" and 79,- respectively, two such grooves'or channels being shownfor each bushing, as this improves the distribution and makes it possible to employ grooves of smaller cross- 7 section. It will also be apparentthat in the case of a very small capacity pump where the relief recesses'are employed inthe bushings on only one side of the gears; then thebushings on the opposite side of the gears will i not require any co-axially extending channels or grooves.

Also, in order for the pressure chambers57, 57a and. 58 to be effective to perform their function, the same must" be placed in communication with a source of high'pres sure. This-is accomplished by providing axially extend ing-channels or 'grooves 80' and 81 inthe pump housing (seeFigure 2) intersecting the outlets 73 and 75, so that high pressure fluid may be conducted; to the respective pressure chambers.

The bore extensions 26, 27, 28-, 29, 30 and Marc placed in'communication with one another through a passage 82, s o that any liquid escaping therearound through the hollow gear journals 32, 33, 34,35, 36"and 37 may Washer-like V be returned to a Zone of lower pressure. elements 83 84 and 85 are-positioned in the bore ex-' tensions 26, 27 and 28, respectively, and are held'in engagement with the ends of the tubular bearingportions 44, 46-and- 48 by springs 86, 87"and' 88 for maintaining initial engagement between the gear facesand the'bushing flanges. As in the aforementioned patent to Lauck et al., a fluid pressure operated flexible coupling, generallyindicated'at 89'is-provided and is placed in com.-

plingmember terminates on itsouter end with a sp'lined or gearconnector- 91 adapted'to cooperate in driving relation with an auxiliary power shaft of an'aircraft" engine or other driving. means.

Inztheprior description, .the end' plates or bushings havebeen specifically described as including flanged por-.

tions and tubular portions and the housing has been so described as formed to receive this particular configuration of bushing. It is to be expressly understood that it is within the scope of this invention, and the appended claims should be so construed, that the bushings or end plates may be constructed with a substantially constant diameter. In such a case, the housing chambers Would necessarily be modified to receive this configuration of bushing. To construct bushings of a substantial constant diameter, it is only necessary to increase the axial length of the flange portion of the bushing shown and described and to exclude or to diminish the axial length of the tubular portion, the sealing ring 56 then being employed to define the pressure chambers.

While this invention has been described in connection with a certain specific embodiment thereof, it is to be understood that this is by way of example, rather than limitation, and it is intended that the invention be defined as the appended claims, which should be given a scope as broad as consistent with the prior art.

We claim:

1. A pum device comprising: a housing containing three adjoining substantially cylindrical chambers having radial end walls, said housing also having a pair of high pressure ports and a pair of relatively low pressure ports, one of each pair of ports communicating with one pair of housing chambers and the other of each pair of ports communicating with another pair of housing chambers, a toothed gear member in each of said housing chambers, one pair of which meshes at the juncture of one pair of said housing chambers and another pair of which meshes at the juncture of another pair of said housing chambers; end plate means disposed in each of said chambers and being associated with said gear members; means defining a pair of flat chordal surfaces on one of said end plate means; means defining a flat chordal surface on each of the other end plate means, said end plate means being so disposed that each end plate means has a fiat chordal surface thereof cooperating with a flat chordal surface of its adjacent end plate means, said end plate means including front faces cooperable with the adjacent side faces of the associated gear members, said front faces and said side faces constituting pairs of adjacent faces which provide a pumping seal between said gear members and said end plate means, said front faces being subject to the pressures in said housing, at least one of said end plate means also having a back face normally spaced from the adjacent'radial end walls of the associated housing chamber and having a portion cooperable with said housing to provide a pressure space at the back of said end plate means; and means establishing communication between the corresponding one of said high pressure ports and said pressure space to subject the back of said end plate means to the pressure in said high pressure port to maintain said pumping seal.

2. A pump device comprising: a housing containing three adjoining substantially cylindrical chambers having their axes parallel and having radial end walls, said housing also having a pair of high pressure ports and a pair of relatively low pressure parts, one of each of said pair of ports communicating with one pair of said housing chambers and the other of each of said pair of ports communicating with another pair of said housing chambers, a toothed gear member in each of said housing chambers, one of which comprises a drive gear and the other two of which comprise driven gears, said drive gear meshing with one of said driven gears at the juncture of said one pair of said housing chambers and said drive gear meshing with the other of said driven gears at the juncture of said another of pair of said housing chambers; end plate means disposed in each of said chambers and being associated with said gears; means defining a pair of flat chordal surfaces on the end plate means associated with said drive gear and a flat chordal surface on each of the other end plate means, said end plate means being so disposed that each end plate means has a flat chordal surface thereof cooperating with a flat chordal surface of its adjacent end plate means, said end plate means including front faces cooperable with the adjacent side faces of said associated gear members, said front faces and said side faces constituting pairs of adjacent faces which provide a pumping seal between said gear members and said end plate means, said front faces being subject to the pressures in said housing, said end plate means associated with said driven gears also having back faces normally spaced from the adjacent radial end wall of the associated housing chambers and having portions cooperable with said housing to provide pressure spaces at the back of said last-named end plate means;

and means establishing communication between the associated high pressure ports and said pressure spaces to subject the backs of said end plate means associated with said driven gears to the pressure in the respective high pressure ports to maintain said pumping seals.

3. A pump device as recited in claim 2, and including a relief recess in one face of each pair of said pairs of adjacent pumping seal providing faces, said relief reesses being disposed inwardly of the root of the teeth of said gear members, respectively, to limit the sealing area between said side faces of said gear members and said front faces of said end plate means, and means establishing communication between said relief recesses and a zone under less pressure than pressure in said high pressure ports.

. References Cited in the file of this patent UNITED STATES PATENTS 1,656,093 n Baker Jan. 10, 1928 2,157,284 Egersdorfer May 9, 1939 2,412,588 Lauck Dec. 17, 1946 2,420,622 Roth et a1. May 13, 1947 2,511,660 Wilson June 13, 1950 2,526,830 Purcell Oct. 24, 1950 2,550,405 Crosby Apr. 24, 1951 2,645,901 Elkins July 21, 1953 2,645,903 Elkins July 21, 1953 2,728,300 Stoermer Dec. 27, 1955 2,765,749 Mosbacher Oct. 9, 1956 

